An Ecological Study of Arthropod Populations on Apple in Northeastern Wisconsin: Species Affecting the Fruit1

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Abstract
The effect of insect populations on fruit was studied in a mature apple orchard under a natural and 2 artificial environments from 1959 through 1962. About 15, approximately 2%, of the 763 species collected from the orchard injured the fruit directly. Ninety-nine to 100% of the apples in the check and captan environments were injured each year, with the plum curculio, Conotrachelus nenuphar (Herbst); apple maggot, Rhagoletis pomonella Walsh; and codling moth, Carpocapsa pomonella (L.), causing most of the injury, in that order. Fruit injury by other species in the check and captan environments was insignificant. Injury in the DDT-captan block was generally low except for that caused by larvae of red-banded leaf roller, Argyrotaenia velutinana (Walker), and of eye-spotted bud moth, Spilonota ocellana (Denis and Schiffermuller), which progressively increased each year. Apple scrab, Venturia inequalis (Winters), was an important factor in the natural (check) environment, affecting tree growth, fruiting, and insect populations. The last mentioned were generally favorably affected in the captan environment, and adversely so in the DDT-captan. Fruit production increased substantially from the check to the captan and DDT-captan blocks with an average yield ratio of 1:1.2:2.1, respectively for the 4-year study. An additive effect was obtained with the use of DDT in the DDT-captan block, which was greater than the combined effect of scab and insect population suppression, resulting in increased tree vigor and fruit set which improved each year.

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